This invention relates generally to a rubber composition and more particularly concerns a rubber composition containing a phyllosilicate mineral filler.
The precise formulation of any elastomeric compound depends on its intended end use. Different end uses require very specific mechanical properties. To a degree, the choice of filler and agent for coupling the elastomer and filler determines the mechanical properties of the elastomeric compound. For example, the use of organosilane coupling agents generally of formula I shown hereinbelow, in conjunction with phyllosilicate minerals as extending or reinforcing fillers in natural or synthetic elastomer compositions, is well known in the art--especially as represented by Sample et al., U.S. Pat. No. 4,260,498, which in its entirety is specifically incorporated herein by reference. Alexander et al., U.S. Pat. No. 2,801,186 and Doran et al., U.S. Pat. No. 3,737,334 also contain illustrative disclosures. In such cases, the organosilane serves to improve the overall mechanical properties of the rubber compositions. In use, the functional organic groups hydrolyze in the presence of moisture typically found on the surface of the minerals to form silanols which react with or otherwise condense in the presence of silica, clay or metal oxide surfaces. To be effective in this respect, the silane coupling agent must be reactive with both the polymer and filler. The coupling agent may be applied to the filler in a separate pre-treatment step, or it may be added directly during elastomer compounding.
Amines have also been disclosed generally for use with phyllosilicate mineral fillers or pigments. Hall, U.S. Pat. No. 2,713,572; Lundsteb, U.S. Pat. No. 2,979,528; Dohman et al., U.S. Pat. No. 3,298,849; Brockmann et al., U.S. Pat. No. 3,925,095; Russell et al., U.S. Pat. No. 3,994,742; Chuiko et al., U.S. Pat. No. 4,121,946; and Compton, U.S. Pat. No. 4,137,092, contain illustrative disclosures. In particular, N,N,N',N'-tetra-2-hydroxypropyl-ethylenediamine, marketed as Quadrol by Wyandotte Chemical Co., and N,N,N',N'-tetra-(2-hydroxybutyl)-ethylenediamine and N,N,N',N",N'",N"",N""-hepta-(2-hydroxybutyl)-tetraethylenepentamine, designated as Nalco L-1718 and Nalco L-1782, respectively, by Nalco Chemical Co., have been disclosed as specific additives for use with talc fillers to develop with highest degree of reinforcement in rubber compositions.
Thus, the use of a phyllosilicate mineral filler in conjunction with either an organosilane or a polyhydroxylated polyamine has been disclosed for use in rubber compositions. However, the use of a phyllosilicate mineral filler in conjunction with both an organosilane and an amine has not heretofore been disclosed for use in rubber compositions. Furthermore, in spite of the known efficacy of organosilanes or amines in rubber compositions, efforts continue to discover alternatives or improvements to known organosilanes and amines. A problem of using such additives as organosilanes or amines in rubber compositions is their relatively high cost. It is therefore desirable to reduce the amount of such agents in rubber compositions without also reducing their effect on the mechanical properties of the rubber compositions.